The present invention relates to a fixing apparatus which is used in apparatuses using a toner, such as a copying machine and printer, and which fixes a toner image.
A fixing apparatus incorporated in a copying machine using an electrophotographic process heats and melts a developer or a toner formed on a transferred member to be fixed, and fixes the toner onto the transferred member to be fixed. Widely known examples of a method of heating the toner usable in the fixing apparatus include: a method of using radiant heat obtained by turning on a filament lamp; a flash heating method of using a flash lamp in a heat source; and the like. Additionally, in recent years, a fixing apparatus in which an induction heating apparatus is used as a heating source has been brought in practical use. Moreover, in many cases, a heating (fixing) roller with a heater set therein, and a pressure-rised roller pressed onto the heating roller at one point of an outer periphery of the heating roller at a predetermined pressure are used. According to the structure, it is easy to efficiently supply the heat from the heating source to the toner, and to apply a pressure for fixing the molten toner onto the transferred member to be fixed.
Additionally, in many of the toners used in a copying machine and a printer, a pigment or a dye is coated with a thermally fusible resin, and formed in a granular form or a powder. Therefore, in many cases, in a portion of the fixing apparatus brought in contact with the molten toner, a toner unfixed onto the transferred member to be fixed remains. Therefore, many fixing apparatuses in each of which a cleaning apparatus is added to the heating (fixing) roller brought in contact with the toner have been practically used.
A known general method of cleaning the fixing roller includes, bringing felt into contact with an outer peripheral surface of the heating roller; or supplying oil to inhibit the toner from adhering to the heating roller. Additionally, with the use of felt, since the toner adheres to a portion in contact with the heating roller, a method of forming the felt in a roller shape and inhibiting the toner from adhering to one position has been practically used.
On the other hand, it has been confirmed that even with the use of felt having the roller shape, the amount of fixable toner is reduced and an image defect is generated during a maintenance cycle. The image forming speed of the copying machine or the printer is enhanced, and/or the maintenance cycle of the copying machine or the printer is lengthened. Moreover, the felt with much toner adhering thereto is pressed onto the heating roller for a long time. These cause a problem that the surface of the heating roller is damaged.
To solve the problem, a web cleaning method has been brought in practical use, which includes, forming the felt in a web shape, and changing (displacing) a position of the felt contacting the heating roller in accordance with a total number of times of image formation (after elapse of a predetermined time).
With the use of the felt having the web shape, in a structure for successively taking up the web with the toner adhering thereto, when an amount of web is set in accordance with the maintenance cycle, the time to change the cleaning apparatus can be set. Additionally, the web is sometimes coated with oil for inhibiting the toner from adhering to the heating roller.
However, when the web shaped felt is used, the feed amount of web is constant. Therefore, immediately after the copying machine or the printer is turned on, such as at the beginning of the day (morning), temperature in the apparatus is low. Particularly, in low-temperature environments such as winter and high latitudes, the fixing apparatus reaches a predetermined standby temperature, but the temperature of the transferred member to be fixed or the toner is lower than an assumed temperature in many cases.
When an image forming output is output in this state, fixability of the toner fixed onto the transferred member to be fixed is close to a lower limit. Therefore, much toner adheres to the heating roller in many cases. This causes a problem that the amount of toner adhering to the web shaped felt increases as compared with the amount of toner adhering to the felt under normal use conditions.
Thereby, the felt becomes dirty in an accelerated manner. Regardless of the use of the taken-up web, there is a problem that the generation of the image defect and damaged heating roller cannot completely be eliminated.
Moreover, when the continuous image formation is repeated and the temperature of the heating roller of the fixing apparatus lowers, an interval of the supplying of the transferred member to be fixed and number of times of image formation are reduced or the supplying and image formation are stopped. Even in the copying machine or the printer in which this method is used, the feed amount of the web is constant.
Therefore, similarly as the above-described low-temperatures, the amount of the toner adhering to the heating roller increases as compared with the amount of the toner adhering under the normal use conditions.
Additionally, many copying machines and printers are accompanied with a pre-run operation of allowing the heating roller to idle in order to make heat distribution uniform, while the heating roller of the fixing apparatus is heated. Even in this case, the feed amount of the web is constant. Therefore, when much toner adheres to the heating roller, the amount of the toner fixed to the web disadvantageously increases. There is another problem that during the supplying of the oil from the web, the oil runs out and the recovered toner adhering to the web adheres to the heating roller again. Even in this case, as described above, the image defects and damaged heating roller are easily generated.
An object of the present invention is to provide a fixing apparatus in which toner can be prevented from adhering to a print out output onto a member to be fixed.
According to the present invention, there is provided a fixing apparatus comprising:
a heating mechanism including:
a heating object which is either a hollow cylinder or an endless belt, and in which a predetermined heat is supplied to a thermally fusible material and a base material holding the thermally fusible material, and either a peripheral surface of the cylinder or a belt surface of the belt, constituting the heating object, is moved at a predetermined speed;
a pressure supply mechanism which supplies a predetermined pressure to the heating object with the thermally fusible material and base material between the pressure supply mechanism and the heating object, and whose peripheral surface is followed and moved by moving either the peripheral surface of the cylinder or the belt surface of the belt, constituting the heating object, at the predetermined speed;
a heating object heating mechanism which is set in the heating object, and allows the heating object to generate heat;
a thermally fusible material recovering member which is brought in contact with the peripheral surface of the cylinder or the belt surface of the belt, constituting the heating object, at the predetermined pressure, and which can recover the thermally fusible material adhering to the peripheral surface of the cylinder or the belt surface of the belt;
a thermally fusible material recovering member renewing mechanism to move a region of the thermally fusible material recovering member brought in contact with the peripheral surface of the cylinder or the belt surface of the belt, constituting the heating object, at the predetermined pressure by a predetermined amount, when a predetermined amount of the thermally fusible material is absorbed by the thermally fusible material recovering member; and
a heating object temperature detecting mechanism which detects a temperature of the peripheral surface of the cylinder or the belt surface of the belt, constituting the heating object; and
a thermally fusible material recovering member renewing mechanism control apparatus which moves the region of the thermally fusible material recovering member brought into contact with the peripheral surface of the cylinder or the belt surface of the belt, constituting the heating object, at a predetermined timing.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.